Image forming systems with gimbaled retard feeder device

ABSTRACT

An image forming system may include a photoreceptor, a sheet feeding apparatus and a retard feeder device that includes a feed roll, retard roll and nudger roll. The retard feeder device transfers a sheet of paper from the sheet feeding apparatus, through the sheet imaging media registration system and on to the photoreceptor. The retard roll is mounted in a loading bracket to allow the Retard Rollers to be loaded against the Feeder Rollers. The loading bracket is mounted on a pivot pin so that the retard rollers can pivot to maintain equal pressure against both feed roll. A retard feeder device may include a bracket, a feed roll assembly that includes two tires, a retard roll assembly that includes two tires and a nudger roll assembly. The retard roll loading bracket is fastened to a pivot pin so that the retard rollers can pivot to maintain an equal pressure between the tires of the retard roll assembly and the tires of the feed roll assembly.

BACKGROUND

The disclosure relates to image forming systems, and more particularlyto a retard feeder device that may be used in the image forming systems.

Retard feeders may be used in image forming systems to advance orseparate an image receiving medium, such as a substrate or sheet ofpaper, from a storage device or tray that holds the image receivingmedium. The retard feeder may include individual rolls. For example, theretard feeder may include a feed roll assembly, retard roll assembly anda nudger roll assembly. The feed roll assembly is positioned oppositethe retard roll assembly, and each roll assembly often may includeeither two rollers or tires or a single wide roller. The feed and retardroll assemblies contact each other forcibly to create a nip. The nudgerroll assembly is forcibly positioned on top of a stack of paper andfrictionally nudges the top sheet [or sheets] into the Feeder-RetardRoller Nip. The feed roll assembly is driven so that they advance thesheet of paper out of the media supply tray. The retard roll is notdriven in a semi-active retard feeder, but the retard roll may include adrag clutch. Maintaining an equal load between the two Feeder and RetardTires is essential to maintaining reliable feeding operation andminimizing media skew or rotation.

The drag clutch establishes a well controlled frictional drag torque onthe retard roll assembly. It permits the retard roller assembly torotate when enough frictional drive force is place on the retard roll bya sheet of paper or other like imaging media being driven through theFeeder-Retard Roller Nip. This is the case when a single sheet ofimaging media has entered the Feeder-Retard Nip. The single sheet is fedwith the feeder roll assembly while the retard roll assembly is rotatedby the passing of the single sheet. If not enough friction is placed onthe retard roll, the retard roll does not rotate and it willfrictionally hold back or ‘retard’ the sheet. This is the case when twoor more sheets of imaging material enter the Feeder-Retard Nip. Thus,the drag clutch may operate as a drag brake. For a single sheet of paperto through the Feeder-Retard Nip, the Feed Roller Drive Force on thesheet must be capable of overcoming the Retard Drag Torque. However, iftwo sheets of paper, e.g., a multi-feed, are advanced from the papertray through the Feeder-Retard Nip, the Retard Drag Torque will holdback or retard the bottom sheet(s) as long as the Drag Force on theRetard Roll is greater than the sheet to sheet friction.

SUMMARY

The feed roll assembly, retard roll assembly and the nudger rollassembly of the retard feeder device are generally positioned parallelto each other but the feed and retard roller assemblies need to beprecisely parallel to each other because they are loaded against oneanother to create the nip. The parallel alignment of the feed rollassembly and retard roll assembly is extremely important because equalpressure must exist between both pairs of feed and retard roller tiresor both sides of a single wide roll nip so that paper is fed into aimage forming system from a storage device with very limited skew.Minimizing skew is important so as to not over stress the Registration &Deskew System, located in the Image Forming System.

In order to acceptably align the feed roll assembly axis and retard rollassembly axis to each other, and create the equal pressure in bothfeed/retard roll nips, the composition or Durometer of conventionalrollers or tires may be altered or reduced to allow the tire deformationto adjust for a lack of parallel alignment and produce an appropriatelybalanced nip pressure across both feeder/retard tire nips. However, whenthe tires are formed of harder or higher Durometer to provide betterwear resistance and roller life, the alignment of the feed and retardroll assemblies becomes more sensitive and unequal pressure may stillexist between the feed and retard roll tire nips. Moreover, somematerials used for the tires are expensive and difficult to manufactureaccurately enough to produce the necessary parallelism. If a uniformpressure, or nip force, does not exist between both feed roller and theretard roller assemblies, a non uniform drive force will be produced bythe two feeder/retard tire nips. This imbalanced drive force can causeprint media skewing or rotation. The low drive force can also allow theretard roller assembly to slip or even stall, causing the leading edgeof a sheet entering the feeder/retard tire nip to stub on the stalledretard roll and misfeed. A paper jam results from the misfeed becausewhen the leading edge of the print media or paper stubs on the stalledretard roller tires, it rolls over or folds under and does not enter thefeeder/retard tire nip.

Thus, in accordance with various exemplary embodiments, a retard feederdevice may be connected to a gimbal, e.g., a pivot pin, to allow theretard roll assembly to pivot into parallel alignment with the feederroll assembly and create uniform pressure between the two sets of tires.Using the gimbal allows longer life higher Durometer materials and/orless expensive manufacturing processes to be used for the tires becausethe gimbal ensures proper alignment and equal pressure between the feedand retard roll assemblies.

In various exemplary embodiments of the disclosure, an image formingsystem may include a photoreceptor, a Registration-Deskew station and asheet feeding apparatus such as a retard feeder device. Such a retardfeeder device will include a feed roll assembly, a retard roll assemblyand a nudger roll assembly. The retard feeder device transfers a sheetof paper from the sheet feeding apparatus storage tray to theRegistration-Deskew Station and then to photoreceptor for imaging. Theretard roll is mounted to a retard roller assembly loading bracket andforcibly positioned against the feed roller assembly.

A retard feeder device may include a bracket, a feed roll assembly thatincludes either two widely spaced tires or a single wide tire, a retardroll assembly that includes either two widely spaced tires or a singlewide tire and a nudger roll assembly. The retard roll loading bracket isfastened to a gimbal or pivot pin so that the retard roll assemblypivots into parallel alignment with the feeder roll assembly to maintainan equal pressure between the tires of the retard roll assembly and thetires of the feed roll assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the systems and methods according tothe invention will be described in detail, with reference to thefollowing figures, wherein:

FIG. 1 shows an exemplary diagram of an image forming system thatincludes a retard feeder device;

FIG. 2 shows an exemplary diagram of the retard feeder device positionedon a feed head frame;

FIG. 3 shows an exemplary detailed diagram of the retard feeder device;and

FIG. 4 shows an exemplary system without a gimbaled retard pivot.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an exemplary diagram of an image forming system 100 thatincludes a retard feeder device. The system includes a belt 10 having aphotoconductive surface 12 deposited on a conductive ground layer 14.The photoconductive surface 12 may be made from a photo responsivematerial, for example, one including a charge generation layer and atransport layer. The conductive layer 14 may be made from a thin metallayer or metallized polymer film that is electrically grounded. The belt10 moves in the direction of arrow 16 to advance successive portions ofphotoconductive surface 12 sequentially through the various processingstations disposed about the path of movement thereof. The belt 10 may beentrained about a stripping roller 18, tensioning roller 20 and driveroller 22. The drive roller 22 may be mounted rotatably in engagementwith belt 10. A motor 24 rotates roller 22 to advance belt 10 in thedirection of arrow 16. The roller 22 may be coupled to a motor 24 bysuitable means, such as gears and/or a drive belt. The belt 10 may bemaintained in tension by a pair of springs (not shown) resilientlyurging the tensioning roller 20 against the belt 10 with the desiredspring force. The stripping roller 18 and tensioning roller 20 may bemounted to rotate freely.

A portion of the belt 10 may pass through a charging station A. At thecharging station A, a corona generating device 26 may charge thephotoconductive surface 12 to a relatively high, substantially uniformpotential. After the photoconductive surface 12 of the belt 10 ischarged, the charged portion may be advanced through an exposure stationB.

At the exposure station B, a controller or electronic subsystem (ESS) 28may receive the image signals representing the desired output image andprocess the signals to convert them to a continuous tone or gray scalerendition of the image that is transmitted to a modulated outputgenerator, for example, the raster output scanner (ROS) 30. Thecontroller 28 may be a self-contained, dedicated minicomputer. The imagesignals transmitted to the controller 28 may originate from a computer,thereby enabling the image forming system 100 to serve as a remotelylocated printer for one or more computers. The image forming system 100may serve as a dedicated printer for a high-speed computer. The signalsfrom the controller 28, corresponding to the continuous tone imagedesired to be reproduced by the printing machine, may be transmitted tothe ROS 30.

After the electrostatic latent image has been recorded on thephotoconductive surface 12, the belt 10 advances the latent image to adevelopment station C where the toner, in the form of liquid or dryparticles, is electrostatically attracted to the latent image usingcommonly known techniques. At the development station C, a magneticbrush development system 38 may advance charged developer material intocontact with the latent image. A magnetic brush development system 38may include two magnetic brush developer rollers such as 40 and 42. Therollers 40 and 42 may advance charged developer material into contactwith the latent image. The developer rollers may form a brush of carriergranules and toner particles extending radially outward. The latentimage on Belt 10 attracts toner particles from the carrier granulesforming a toner powder image thereon. As successive electrostatic latentimages are developed, toner particles are depleted from the developermaterial. A toner particle dispenser 44 dispenses toner particles into adeveloper housing 46 of the development system 38.

As shown in FIG. 1, after the electrostatic latent image is developed,the toner powder image present on the belt 10 advances to the transferstation D. A print sheet 48 is advanced to the transfer station D by asheet feeding apparatus 50. The sheet feeding apparatus 50 may include aretard feeder device 80 that includes a feed roller assembly 81, retardroll assembly 82 and nudger roller assembly 83. The nudger roll 83 maycontact the uppermost sheet of paper in the stack 54 and the rollerassembly rotates to advance the uppermost sheet of paper from the stack54 to the feed roll assembly 81 and retard roll assembly 82. The feedroller assembly 81 and retard roller assembly 82 may separate any doublefed sheets before forwarding the sheet into the Registration-DeskewStation 205. The Registration-Deskew Station may incorporate a set ofclutched stalled Nip Rollers 210 and a Buckle Chamber 215. After beingdeskewed, the fed sheet is driven into a chute 56. The chute 56 maydirect the advancing sheet of support material into contact withphotoconductive surface 12 of belt 10 in a timed sequence so that thetoner powder image formed thereon contacts the advancing sheet at thetransfer station D. The transfer station D may include a coronagenerating device 58 that sprays ions onto the back side of sheet 48 inorder to attract the toner powder image from photoconductive surface 12to sheet 48. After transfer, the sheet 48 continues to move in thedirection of arrow 60 onto a paper transport or conveyor (not shown)which advances the sheet 48 to a fusing station E.

The fusing station E may include a fuser assembly 62 that permanentlyaffixes the transferred powder image to the sheet 48. The fuser assembly60 may include a heated fuser roller 64 and a back-up or pressure roller66. The sheet 48 passes between the fuser roller 64 and back-up roller66 with the toner powder image contacting the fuser roller 64. In thismanner, the toner powder image is permanently affixed to the sheet 48.After fusing, the sheet 48 advances through the chute 68 to output tray72 for subsequent removal from the printing machine by the operator.

After the print sheet is separated from photoconductive surface 12 ofbelt 10, the residual toner/developer and paper fiber particles adheringto photoconductive surface 12 are removed there from at the cleaningstation F. The cleaning station F may include a rotatably mountedfibrous brush in contact with the photoconductive surface 12 to disturband remove paper fibers and a cleaning blade to remove thenontransferred toner particles. Subsequent to cleaning, a discharge lamp(not shown) floods the photoconductive surface 12 with light todissipate any residual electrostatic charge from the image remainingthereon prior to the charging thereof for the next successive imagingcycle.

FIG. 2 shows an exemplary diagram of the retard feeder device 80positioned on a feed head frame 90. As shown in FIG. 2, a gimbal pivotpin 91 is positioned on the feed head frame wall 92 in between the feedhead frame wall 92 and the retard feeder device 80. A traditional feedhead frame 90 could include retard assembly carrier pivot ears on thefeed head frame wall 92. They may be altered or removed so that thegimbaled bracket 94, the retard carrier bracket 95 and the retard rollerassembly, 82 from FIG. 1, is allowed to pivot on the pivot pin 91. Byusing the gimbal pivot pin 91, the Gimbal Bracket 94 and the retard rollassembly 82 is allowed to pivot. The pivoting motion of the retard rollassembly 82 allows the retard roller assembly to be parallel to thefeeder roller assembly. This ensures equal pressure between the tires ofthe feed roller assembly 81 and the tires of the retard roller assembly82, which reduces sheet skew and misfeeds as the individual sheets ofpaper are fed into an image forming system 100 from the stack 54.

In accordance with various exemplary embodiments, the gimbal pivot pin91 may be positioned on the feed head frame wall 92 as shown in FIG. 2.The pivot pin 91 may be fastened to the feed hard frame wall by anyknown fastening means, and the retard carrier bracket 95 of the retardroll assembly 82 located within the retard feeder device 80 may beaxially retained on the pivot pin 91 using a pin thrust fastener 93. Thegimbal bracket 94 may be formed of, for example, aluminum or plastic.The retard roll assembly 82 is mounted in the retard carrier bracket 95which is pivotally secured to the gimbal bracket 94. The carrier pivotaxis 96 is perpendicular to the gimbal pin axis 91. The retard carrierbracket 95 and the retard roller assembly 82 are spring loaded todevelop the required nip force between the feeder and retard rollerassemblies, so that it develops equal pressure on both of the retardroller assembly tires. Because the pivot pin 91 is fastened to the feedhead frame wall 92 perpendicular to the rotational axis of the feed andretard roller assemblies 81 & 82, the pivot pin 91 allows the retardroll assembly 82 to rotate in a direction shown by arrows A in FIG. 3 tocorrect or eliminate any gap between feed roller assembly tires 81 a andretard roller assembly tires 82a. The gimbal pivot pin 91 must bepositioned on the feed head frame wall 92 symmetrically to andvertically above the combined Center of Gravity 97 of the gimbaled parts[the gimbal bracket 94, retard carrier bracket 95 and the retard rollassembly 82] to ensure stability and to provide the necessary uniformpressure between the individual feed and retard tires [81 a/82 a, 81b/82 b].

For example, the gimbal pivot pin 91 must be positioned central betweenthe two feed rolls 81 a-b so that its longitudinal axis points towardthe paper stack 54 and be parallel to the plane of the paper sheets. Ifthe gimbal pivot pin axis is not equidistant between the individual tirenips, the nip loads will not be equal. The gimbal pivot pin 91 allowsthe gimbal bracket 94, the retard carrier bracket 95 and the retard rollassembly 82 to align with the feed roll assembly 81 and apply equal nipforce to both sets of tires. If the retard roll assembly 82 is notnominally balanced, the off center weight may load one roller more thananother. Thus, a balance weight 87, e.g., a counterweight, may beincluded as shown in FIG. 3 to offset an asymmetric moment from the dragclutch 84. The balance weight 87 also forces the center of gravity backto the pivot pin 91 axis. The drag clutch 84 is attached to the retardcarrier bracket 95. The drag clutch is rotationally coupled to theretard roll assembly 82 using gears 86 a-b. The balance weight 87 may beattached to the retard carrier bracket 95.

FIG. 3 shows an exemplary detailed diagram of the retard feeder device.The retard feeder device 80 self-aligns or pivots to contact both feedroller tires with both retard roller tires with a uniform pressure. Asshown in FIG. 3, the retard feeder device 80 may include the feed rollassembly 81, retard roll assembly 82 and nudger roll assembly 83. Thefeed roll assembly 81 may include feed roller tires 81 a-b, and it maybe positioned above the retard roll assembly 82. The retard rollassembly 82 may include retard roller tires 82 a-b. The feed rollertires 81 a-b and retard roller tires 82 a-b may be formed to resembletires and they may be composed of urethane, silicon or other suitablehigh coefficient of friction materials. The drag clutch 84 limits theretard roll assembly 82 the media retarding frictional drag torque androtate when enough friction force is placed on the retard roll assembly82. If not enough friction force is placed on the surface of the retardroll assembly 82, the retard roll assembly 82 does not rotate. Thus, thedrag clutch 84 may operate as a drag brake. The feed roll assembly 81may be driven by a motor (not shown) and suitable gears or belts (notshown). As power is applied to the motor, the motor drives or rotatesthe feed roll assembly.

As shown in FIG. 4, without the gimbaled retard pivot feature, theretard roller assembly 82 is uniformly contacting the feed roll assembly81, possibly indicating a high spot on one of the tires, preventinguniform contact on both nips. However, a gap 88 exists between the feedroller tire 81 b and retard roller tire 82 b because the eccentric tire81 a pushes down on the retard roller assembly 82 and the retard carrierbracket 95. The gap 88 indicates a loss of nip pressure between the feedroller tire 81 b and retard roller tire 82 b caused by the feed rollassembly 81 and retard roll assembly 82 centerlines being rigidly fixedand unable to accommodate high tire spots, tire eccentricities or tirediameter differences. In other words, the feed roll 81centerline to theretard roll 82 centerline side to side spacing remains fixed. Theeccentric tire contact on one side temporarily increases the nip centerdistance on both sides, decreasing or totally eliminating contact on theother tire nip. This creates an unbalanced nip force between the twofeed-retard nips.

With the gimbaled retard pivot, the retard roll assembly 82 self-alignsor pivots to contact both feed roller tires with both retard rollertires with uniform pressure,. The uniformity of the nip pressure isimproved and the gap shown in FIG. 4 is eliminated. Thus, sheet skewingand paper jams that occur in conventional devices are significantlyreduced or eliminated by providing a uniform pressure across bothfeed-retard tire nips.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. An image forming system, comprising: a photoreceptor; a sheet feedingapparatus; and a retard feeder device that includes a feed rollassembly, a retard roll assembly and a nudger roll assembly, the retardroll assembly including a retard roll tire nip, the feed roll assemblyincluding a feed roll tire nip, the retard feeder device transferring asheet of paper from the sheet feeding apparatus to a registration-deskewstation and on to the photoreceptor; and the retard roll assemblymounted on a gimbal pivot pin so that the retard roll assembly pivotsinto alignment with the feed roll assembly to maintain equal pressurebetween both of the feed and retard roll tire nips.
 2. The image formingsystem of claim 1, wherein the retard roll assembly pivots either in aclockwise or counter-clockwise direction around the gimbal pivot pin. 3.The image forming system of claim 1, wherein the gimbal pivot pin ispositioned in between a feed head frame and the retard feeder device. 4.The image forming system of claim 3, the retard roll assembly comprisinga carrier bracket, wherein a gimbal bracket is connected to the carrierbracket and is fastened to the pivot pin using a fastener.
 5. The imageforming system of claim 4, comprising a drag clutch attached to thecarrier bracket of the retard roll assembly.
 6. The image forming systemof claim 5, wherein the drag clutch allows the retard roll assembly toovercome a frictional drag torque of the retard roll assembly and rotatewhen a sufficient friction force is place on the retard roll assembly.7. The image forming system of claim 5, comprising a balance weightconnected to the carrier bracket of the retard roll assembly, thebalance weight offsetting an asymmetric moment from the drag clutch andforcing a center of gravity back to an axis of the gimbal pivot pin. 8.The image forming system of claim 7, wherein the feed roll assembly andretard roll assembly are formed as feed roll and retard roll tires,respectively, and the retard roll assembly having the carrier bracket isspring loaded so that the retard roll assembly develops equal pressureon the feed and retard roll tires.
 9. The image forming system of claim7, wherein the feed roll assembly and retard roll assembly are formed astires composed of urethane, silicon or a high coefficient frictionmaterial.
 10. The image forming system of claim 9, wherein the nudgerroll assembly contacts the sheet of paper and rotates to advance thesheet of paper to the feed roll assembly and retard roll assembly fromthe sheet feeding apparatus.
 11. A retard feeder device, comprising: afeed head frame; a feed roll assembly that includes either two tires orone wide roller; a retard roll assembly that includes a carrier bracket,a gimbal bracket, and either two tires or one wide roller; and a nudgerroll assembly, the retard roll assembly fastened to a gimbal pivot pinso that the retard roll assembly pivots to maintain an equal pressurebetween the tires or roller of the retard roll assembly and the tires orroll of the feed roll assembly.
 12. The retard feeder device of claim11, wherein the retard roll assembly including the carrier bracket andthe gimbal bracket is fastened to the pivot pin using a fastener. 13.The retard feeder device of claim 12, wherein the retard roll assemblypivots either in a clockwise or counter-clockwise direction around thegimbal pivot pin.
 14. The retard feeder device of claim 13, wherein theretard roll assembly having the carrier bracket is connected to gimbalpivot pin using the gimbal bracket.
 15. The retard feeder device ofclaim 11, comprising a drag clutch connected to the carrier bracket. 16.The retard feeder device of claim 15, wherein the drag clutch allows theretard roll assembly to overcome frictional drag torque and rotate whena sufficient frictional force is place on the retard roll assembly. 17.The retard feeder device of claim 16, comprising a balance weightconnected to the carrier bracket, the balance weight offsetting anasymmetric moment from the drag clutch and forcing a center of gravityback to an axis of the gimbal pivot pin.
 18. The retard feeder device ofclaim 17, the feed roll assembly comprising tires, wherein the retardroll assembly is spring loaded so that the retard roll assembly developsequal pressure against the feed roll assembly tires.
 19. The retardfeeder device of claim 18, wherein the tires are composed of urethane,silicon or a high coefficient friction material.
 20. The retard feederdevice of claim 19, the retard roll assembly including a retard rollnip, the feed roll assembly including a feed roll nip, wherein thenudger roll assembly contact a sheet of paper and rotates to advance thesheet of paper to the feed roll and retard roll nips from a stack ofpaper.